OpenSSH version 8.1 compatibility

Is WinSCP 5.19.4 (Build 11829 2021-10-24) fully compatible with OpenSSH version 8.1?
If not, what versions are compatible?

Thank you!

We are not aware of any incompatibility with OpenSSH 8.1.

Another quick question than – will WinSCP 5.19.4 connect to the server with disabled support for SSH-RSA1 algos, but has SSH-RSA2- 256-bit algos enabled?

The rsa-sha2-256 is supported since WinSCP 5.20 only:
Issue 1952 – Support rsa-sha2-256 and rsa-sha2-512 SSH public key algorithms
Always use the latest version of WinSCP.